This invention relates generally to continuous physical removal of at least one non-soluble lower specific gravity oil from an aqueous liquid medium and more particularly to process equipment further enabling a plurality of such oil materials to be separated and collected in a more effective manner, including the method of operating such process equipment.
Various metalworking and metalforming processes which include broaching, grinding, milling, rolling, stamping and turning now employ liquid coolants and other treatment liquids frequently utilizing an aqueous medium. Such medium often comprises a physical mixture of one or more non-soluble lower specific gravity oils dispersed in water which can further include suspended solids from the particular metal being processed after being used. Process equipment is also known whereby certain suspended oils and the suspended solids can be physically separated from the various treatment liquids in a continous manner before any reuse or disposal. One type oil separation system for such purpose employs a multicompartment tank having an inlet side for sequential removal of solids and floating oil with a subsequent processing side to remove dispersed oils from the influent mixture. A floating skimmer device is provided on the inlet side to first pick up free floating tramp oils and with oil constituents that still remain dispersed in said liquid medium being next removed therefrom in an intermediate compartment by a combined action of coalescence and gravity. More particularly, a medium is therein employed which collects tiny oil particles dispersed in the liquid medium to form much larger droplets having sufficient buoyancy to break free and rise to the liquid surface for a single separation thereat by fixed gating means such as a weir device. The now clarified liquid medium is pumped into further tank compartments enabling removal of still remaining soluble organic materials by ultrafiltration before its discharge into conventional disposal means such as a sewer. A simpler known coolant and washwater recycling system employs a two compartment separator tank having an inlet side which contains the coalescing medium along with the floating skimmer device in an entrance compartment to effect a separation of the floating oil constituents thereat. A bag filter can also be employed in the inlet compartment to effect a further removal of any suspended solids in the liquid medium. Utilization of an oleophilic material for the coalescing medium is said to accelerate separation of oil and water phases in the liquid medium being treated so as to permit a single separation to take place in a much smaller tank than would be required by gravity action alone. Continuous passage of the now clarified liquid medium to an exit compartment is provided with first fixed weir means whereby the exiting liquid passes under said weir device and then proceeds over a second fixed weir device to the tank outlet means. Separator systems of this type are also reported to be used for disposal of the liquid medium after treatment into conventional waterways.
A still third known process equipment of this general type is said to remove free floating, dispersed and loosely emulsified tramp oils from metal working coolant reserviors and parts washers. The dirty liquid medium is treated in a tank member divided into entrance, intermediate and exit compartments for continuous passage of the oil bearing aqueous liquid therethrough by action of associated liquid pumping means. A floating skimmer device in the dirty liquid reservoir collects surface tramp oil which is pumped to the entrance compartment of the separator tank wherein free floating oils, bio-slimes and solids settle out. Fixed gating means are provided at the exit end of said compartment enabling the liquid medium to overflow into an intermediate compartment section having a vertically slanted plate stack which removes dispersed and loosely emulsified tramp oils and settles finely dispersed suspended solids. The liquid medium passes from said intermediate compartment section under fixed gating means to an exit compartment section having adjustable gating means which enable overflow of the separated oils and bio-slimes into a suitable waste oil container. A fixed effluent discharge weir controls liquid level in the separator tank while additional gating means returns the cleaned liquid medium to its initial reservoir. Selling or recycling of the separated tramp oils is said to be possible by this equipment manufacturer.
Considerable need still remains for a more effective as well as individual separation of these oils from various aqueous treatment liquids to reduce new material purchases as well as to reduce environmental contamination. From the standpoint of reducing environmental contamination alone it has been reported that aromatic constituents commonly found in the petroleum hydrocarbons now being used in many metalworking and metalforming fluids are toxic to all organisms. The hydrocarbons are lyophilic and because they are not metabolized or excreted, tend to accumulate in the fatty tissues of mammals. Contamination of shellfish is particularly of concern because they are consumed in great quantities by humans. Large doses of these aromatic hydrocarbon compounds can be lethal while sublethal quantities can have a variety of physiological effects, including carcinogenicity. To still further illustrate such concern, the compound benzopyrene found in coal tar has already been proven by Ames test to produce cancer.
It is an object of the present invention, therefore, to provide improved means for continuous physical recovery of at least one non-soluble lower specific gravity oil from an aqueous liquid medium.
It is another object of the present invention to provide such improved recovery means whereby a plurality of oils having different specific gravities can be individually separated from the liquid medium and collected.
It is still another object of the invention to provide process equipment utilizing a single tank member wherein different specific gravity oils can be separately collected for either reuse or waste disposal.
A still further object of the invention is to provide such processing equipment in a manner so that oil having essentially the same specific gravity can be separated from the liquid medium and removed at multiple collection sites as well as permitting oil of dissimilar specific gravity to be similarly collected.
Another object of the invention is to provide such process equipment whereby oil floating on the surface of the entering liquid medium is first collected, then followed by collecting oil initially dispersed in said liquid medium, and still further followed by collecting any remaining oil floating on the liquid surface.
Still another object of the invention is to provide a novel method for the collection of oil material from an aqueous liquid medium.
These and other objects of the present invention will become more apparent upon considering the following detailed description for the present invention.